The conventional model, well known to those of ordinary skill in the art, for managing cross-connects in a digital switching fabric is defined by the International Telecommunications Union (ITU) and Telecordia standards bodies. A cross-connect object is defined in the standards as a managed connection between two or more termination points (TPs), or connection termination points (CTPs). Digital cross-connects can be either unidirectional or bi-directional. Unidirectional cross-connects can be either point-to-point or point-to-multipoint (i.e. multicast). A specific example of the prior art is disclosed in the ITU M3100 network object model, which includes the following object definitions: ITU M3100 Termination Point—a physical or logical termination point on a switching device, defining the physical or logical point of origination and/or point of termination for a connection, where the termination point object can be either unidirectional or bi-directional, in the unidirectional case there existing both source termination points and sink termination points; ITU M3100 Cross-Connect—an object that defines the interconnection between two or more termination points; and ITU M3100 Multicast Cross-Connect—a cross-connect object that supports only unidirectional termination points, but which supports multiple terminating sink termination points.
The ITU M3100 cross-connect configuration is illustrated in FIG. 1, and, specifically, a point-to-point cross-connect between two termination points. The figure illustrates two termination points 10 linked via a cross-connect 12, a connectivity pointer 14, and two cross-connect object pointers in the termination points and two from/to termination pointers in the cross-connect objects 16.
The ITU M3100 multicast configuration is illustrated in FIG. 2. The figure illustrates a plurality of termination points 10 linked to a plurality of cross-connects 12 via a plurality of cross-connect object pointers in the termination points and from/to termination pointers in the cross-connect objects 16. The plurality of cross-connects 12 are linked to a multi-point cross-connect 18 and the plurality of termination points 10 are linked to an additional termination point 10 via a plurality of connectivity pointers 14. Finally, the multi-point cross-connect 18 is linked to the additional termination point 10 via a cross-connect object pointer in the termination point and from/to termination pointer in the cross-connect object 16.
The standards-based prior art, for example, requires that the input for a selector switch be a termination point. The input termination point of a cross-connect, however, can change based upon well-defined criteria, i.e. a failed signal or user-initiated switch. A roll operation (point-to-point unidirectional sink termination) with the ITU M3100 cross-connect configuration in bridge-and-roll is illustrated in FIG. 3. The figure illustrates a plurality of termination points 10 and a cross-connect 12 within the digital switching fabric 20. It should be noted that ITU M3100 Amendment 5 provides a method of converting bi-directional cross-connects to unidirectional point-to-point cross-connects, and converting unidirectional point-to-point cross-connects to multicast cross-connects. The Telecordia standards body provides a similar model for cross-connects in a switch fabric intended for digital communications.
Conventional bi-directional digital cross-connect designs relate a single bi-directional termination point to another single bi-directional termination point and allow for the management of the connection through software. Similarly, conventional unidirectional digital cross-connect designs relate a single unidirectional source termination point to one or more (in the multicast case) unidirectional sink termination points. Conventional cross-connect models inherently limit the scaling of the cross-connect matrix due to the fact that the cross-connect relationship is always defined between termination points. One limitation addressed by the methods and systems of the present invention is the case of drop-and-continue multicast connections, which must be protected (i.e. have redundant tributaries) within the network. Other applications addressed by the methods and systems of the present invention include signaled network connection, bridge-and-roll, test access point, and circuit switching applications, among others.
FIG. 4, related to dual head-end video broadcasting, illustrates such a network topology that is addressed by the methods and systems of the present invention. In this example, traffic originates at a video server “head end” and is broadcasted to client equipment at each node and continues around the ring. A redundant path traverses the ring in the opposite direction. Traffic is selected from the path with the highest relative signal quality. Because the path is selected based upon relative signal quality, each protected network element (N or NE) 22 must be accessible to both video head ends.
Referring to FIG. 5, using the standards-based cross-connect designs described above, such a network topology would not be possible. An M3100-style multicast cross-connect with a selectable input (via selector 24) is implemented, where the input is the termination point 10 in the ring. This, however, does not provide “drop-and-continue” in both directions on the ring, as traffic only flows from the direction that is selected., i.e. from server 1 or from server 2, not both.
One possible solution using the standards-based model involves performing the selection at the multicast sink termination points when the relative signal quality changes on the input “source” termination points. This requires that each client-facing sink termination point have a pointer to a given multicast cross-connect in order to keep track of its selector state. This is illustrated in FIGS. 6 and 7. Any unprotected drop termination points, however, would have to be managed separately and would further complicate the problem.
The constructs described above become complicated and difficult to manage using conventional methods and systems. The systems must be capable of managing the selector states of the individual drop termination points, and be capable of coordinating the settings of all of the selector states when the signal quality at the server-facing termination points change relative to one another.
Thus, what is still needed in the art are methods and systems for managing matrices of connections within digital switching fabrics, where the sources and sinks in a matrix of connections are the unidirectional connection termination points and novel unidirectional virtual connection point objects. In order to be useful, a virtual connection point must be a logical object that is maintained in software that defines a connection between real network resources, as well as other logical objects. The virtual connection point must have a point of input selection. Due to its unidirectional nature, it would act as a source connection point for multicasting.